Many commercial and industrial processes create the possibility for explosions, even the warehousing of combustible dusts and products that release combustible vapors presents such a risk. Such explosions may damage or destroy any structure that is not designed to resist the considerable pressures generated by a dust or vapor explosion. Deflagration vents, blow out panels, explosion panels, or explosion vents have been employed to lessen any damage to a structure housing potentially dangerous processes when an explosive event occurs by allowing the pressure created in such an explosion to escape through deflagration vents rather than deform and destroy the structure. A pressure relief device is a broad term encompassing all the venting devices described above. The above described venting practices are particularly effective in the case of explosions that propagate below the speed of sound, a deflagration. Industry standards such as NFPA 68 in the United States and the ATEX directive, used in Europe, and related harmonized standards in Europe and elsewhere establish requirements for such protective measures.
Because a temperature, climate, and/or clean controlled environment is desired, and even required by some processes, deflagration vents have been employed that maintain the environmental integrity of the structure. Such vents in the past have been held in place by magnets, spring mechanisms, re-settable latches, or have been constructed of frangible materials. Because the physical properties of magnets, springs and latches can change over time and their application for control of deflagration vent release pressure requires on site calibration, start up testing, periodic testing, and maintenance are required. Periodic testing and maintenance can be intrusive, costly and requires the availability of skilled personnel to take responsibility for the function of such pressure relief devices at all times. On the other hand, vents with integral frangible components are destroyed during an explosive event, very strong winds, or other non-explosive pressure differential causing events. This actuation, whether intended due to a predetermined pressure differential, or inadvertent, due to strong winds or unintended contact, often requires the costly replacement of the entire vent device.
In current vent devices, the venting condition, i.e., the relieving of internal pressure, is dependent on the mass and shape of the combined structure forming (1) the release mechanism(s) holding the vent in a pre-venting configuration when installed and (2) the vent structure itself (i.e., the shape and mass of the vent panel, explosion panel etc.). Therefore, the particular venting condition is necessarily dependent on a force load's effect on the combined release mechanism and vent structure. Due to this dependence, the desired set venting pressure must be configured on a case by case basis requiring costly individualized customization for each pressure relief device as well as testing and maintenance of the venting device to assure accuracy of performance.
It is therefore desirable to have a vent device that does not require set up testing, periodic testing, or other skilled maintenance activities, and is not necessarily destroyed during deployment, either by an explosive or other pressure differential causing event. Additionally, there is a need for a vent device, or other pressure relief device, where the set pressure can be controlled by some factor other than the shape and mass of the combined vent shape and structure. This application describes a solution for these problems.